Fuel Cost Calculator: Trip Gas Cost and Fuel Economy

Free fuel cost calculator: the gas cost of a trip from distance, fuel economy (L/100 km, mpg US or UK, km/L) and price per litre or gallon, round trips and cost per person, fuel economy from a fill-up, and an electric car comparison.

Trip distance

Distance in

Trip

Fuel economy — type it in any unit, the others fill in

L/100 km

km/L

mpg (US)

mpg (UK)

Fuel price

Price is per

Currency

People sharing

Fuel

Plan with a map

From

Open directions in Google Maps

Google Maps opens in a new tab with the route; type the distance it shows into Trip distance above. This page does not look up the distance itself, so the places you type go only to Google, and only when you press the button.

Fuel economy from a fill-up

Fill the tank, reset the trip meter, drive, fill it again: the distance driven and the fuel the second fill took give your real economy.

Distance since the last fill

Fuel put in

Compare two cars

Second car's economy

Its fuel price (blank = same)

Distance a year

Electric car comparison

Electric car uses

Electricity price per kWh

Charging loss

Grid CO₂ (g per kWh)

Electric car costs more by

How to calculate the fuel cost of a trip

Fuel needed = distance × fuel use per distance; cost = fuel needed × price. With metric units that is litres = km × (L/100 km) ÷ 100. Example: 350 km in a car using 7.8 L/100 km needs 350 × 7.8 ÷ 100 = 27.3 L; at $1.65 a litre that is $45.05, or $11.26 each for four people. With miles and mpg it is gallons = miles ÷ mpg: 300 miles at 25 mpg = 12 gallons, at $3.50 a gallon $42.00.

Converting fuel economy units

L/100 km is fuel per distance (lower is better); km/L and mpg are distance per fuel (higher is better), so converting between them means dividing a constant by the value. This page uses the exact definitions: 1 mile = 1.609344 km, 1 US gallon = 3.785411784 L, 1 UK (imperial) gallon = 4.54609 L. That gives L/100 km = 235.215 ÷ mpg (US) and 282.481 ÷ mpg (UK), and L/100 km = 100 ÷ km/L. So 30 mpg US = 7.84 L/100 km, while 30 mpg UK = 9.42 L/100 km: a UK gallon is bigger, so the same car shows a higher mpg in Britain.

Common values

CO₂ from burning fuel

Burning a litre of gasoline gives off about 2.31 kg of CO₂, a litre of diesel about 2.68 kg (approximate tailpipe figures; making and moving the fuel adds roughly 15-25% more). For an electric car the page multiplies the electricity from the wall by the grid's carbon intensity, which ranges from under 50 g/kWh (hydro, nuclear: Quebec, Norway, France) to 700+ g/kWh (mostly coal); 400 g/kWh is a rough world average, so change it to your own grid's figure.

Questions

Why does my real economy differ from the sticker?: Official figures come from standard test cycles. Speed (drag rises with the square of speed), cold weather, short trips, air conditioning, roof boxes, tyre pressure and load all change it. The fill-up method above measures your own.
Should I split the cost with passengers?: Splitting fuel is common for car pools and road trips. Put the number of people in People sharing, the driver included. Wear, insurance and parking are not counted here.
Does a round trip just double it?: Yes: Round trip doubles the distance. If the way back is different, add both distances yourself.
How is the electric car break-even worked out?: Yearly fuel cost of the fuel car minus yearly electricity cost of the electric car is the saving per year; the extra purchase price divided by that saving is the years to pay it back. Maintenance, insurance, incentives and resale value are not included.
Is anything I type stored?: Only in this browser (localStorage). Nothing is uploaded; a copied link carries the numbers in the address itself.

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